Electrical indicator



2 Sheets-8heet I. J. W. HOWELL.

ELECTRICAL INDICATOR.

(No ModeL) Patented Mar. 30, I886.

\I \l (I U mam- N. PEYERS. Ptwioiiihvgfipbur. Washington. D. C.

2 Sheets-Sheet 2.

J. W. HOWELL.

ELECTRICAL INDICATOR.

Patented'Mar. 30, 1886.

(No Model.)

I M l I Fries.

JOHN \V. HOYVELL, OF N EYV BRUNSVVIGK, ASSIGNOE TO THE EDISON LAMPCOMPANY, OF HARRISON, NE\V JERSEY.

ELECTRlCAL INDICATOR.

SFECIFICATIQN forming part of Letters Patent No.339,058, dated Ii/Iareh30, 1886.

Application filed December 24, 1585. Serial No. 186,653. (No model.) I

To aZZ whom, it may concern.-

Be it known that I, JOHN \V. HOWELL, of New Brunswick, in the county ofMiddlesex and State of New Jersey, have invented a certain new anduseful Improvement in Electrical Indicators, of which the following; isa specification.

This invention relates to an instrument for indicating changes inelectro-motive force or for measuring the same, and is intendedespecially for use in systems of electric lighting to indicatevariations of electro-motive force, so that the generators may beregulated accordingly.

My instrument is an improvement on that set forth in the patent to O. S.Bradley, N0. 280, 568, dated July 3, 1883, my object being to produce aninstrument operating substantially on the same principle as that in thepatent referred to, but cheaper and more compact in construction, andmore accurate, efficient, and convenient in operation than thatinstrument.

My invention is illustrated in the annexed drawings, in which Figure 1is a theoretical diagram illustrating the principle of my invention;Fig. 2, a diagram which shows also some features of construction; Fig.3, a perspective view or the instrument with part of the case brokenaway, Fig. 4, a view of a portion of the adjustable resistance which Iemploy, and Fig. 5, a diagram of a modification of my invention.

Referring first to Fig. 1, 1 2 are the points of an electric circuit theelectro motive force or difference of potential between which is to beindicated. The parts of the instrument form a Wheatstone bridgeconnected between said points 1 2. In one side of said bridge are aresistance, A, and an incandescing electric lamp, B. In the other sideare a resistance, 0, a resistance, D, and between these two aresistance, E. The galvanometer F is in the bridge between the twosides. One

of its terminals is connected with. the contact a, which travels uponthe coils of the resistance E, whose construction will be presentlyexplained.

The operation of theinstrument may be gen- 5 erally explained withrelation to Fig. 1. The

connection of the galvanometcr to the resistance E is first adjusted sothat the galvanometer-needle stands at zero with the standardelectro-motive force, or that which it is desired to maintain in thesystem. An increase in this electro-motive force increases thetemperature of the carbon conductor of the lamp B, and hence decreasesthe resistance thereof. This destroys the balance of the resistances,and current flows through the galvanometer in the direction ofthe arrowin Fig. 1. The deflection of the galvanometer shows the amount of theincrease in electro-motive force. A decrease in eleotro-motive force,causing an increase in the resistance of the lamp, causes current topass through the galvanometer in the opposite direction, so that thisalso is indicated. In thepatcnt of Bradley,above meir tioned, twoincandescing electric lamps are employed as sensitive resistances, onein each arm of the XVheatstone bridge, and wire reresistances, one ofwhich is adjustable, are also placed one in each arm. In thisarrangement, if the lamps are of equal resistance, the sum of the twowire resistances has to be equal to orgreatcr than the sum of the twolamp-resistances. Further, the wire of each of the wire resistances hasto be of sufficient conductivity to carry the current of the lamp inseries with it. For these reasons a great length of large wire, which isexpensive and occupies a great deal of space, has to be used. In myarrangement, however, as the proportions are A: 15 G D, by making theresistance 1) of fine wire and high resistance, which I can do becauseit does not have to carry the lampcurrent, I can make resistance A ofvery low resistance, and therefore have to use only a short length ofthe heavy wire necessary to carry the lamp-current. The rco sistances Cand E also are made of line wire, and therefore my instrument effects alarge savingin expense of wire and in bulk over the Bradley instrument.I prefer to make the resistance D of about one thousand ohms. Re- 9 5sistance Ais such that the lamp B is not brought to its fullcandle-power, and its permanency is thereby assured. It will be seen, ofcourse, that so much of the resistance E as may be on the right of theadjusting contact forms in reality part of resistance D, while thosecoils which are on the left form part of resistance Fig. 2 betterillustrates the practical arrangement of the circuits. H H represent thebinding-posts, which are the terminals of the instrument. Theresistance-coils are wound upon suitable spools or frames. In thisfigure the resistance-adjusting contact, which is the terminal of theconductor 3, is not shown.

The instrumentitself is shown in Figs. 3 and 4. I is asuitableinclosingbox or case, of wood or other suitable material, with abase-board, 1, which may be attached to a wall or other object. K is asuitable frame, upon which the two sets of resistance-coils O and D arewound. This frame is supported from the side ofthe box by screws 0.Asimilar frame, L, supported in the same way by screws d, carries theresistance-coils B. Coils E are wound upon a bar, M, also carried fromthe sides of the box by screws. (Not shown.) A rod, N, extends parallelto M, and on this is a movable sleeve, e, which has a handle, f, formoving it, said handle passing through a slot, 9, in the front of thebox, and having upon it a pointer, 71., which travels along scale tabove the slot. A set-screw, f, is provided, which sets against rod N,to hold the contact at the point at which it is placed. On its innerside sleeve 6 carries the contact-spring a. The coils E are of insulatedwire, but on one side the insulationis filed or scraped off, and thespring a travels along this bared portion, so that its movement connectsthe galvanometer to different parts of the coil E. At one end (see Fig.4) the end plate, Z, extends out against the front of the case, and ascrew, in, passes through the case, so as to make contact with Z, orbreak it, if the screw is turned. To this screw the wire 3 from thegalvanometer is connected, and thus the galvanometer-shunt may be madeand broken as desired. The galvanometer F is supported from the back orbase board of the case. Its pointer 0 extends out in front of a scale,0, placed behind an opening, P, in the front of the case. The scale issupported by arm 2 1), extending from the galvanometer. Q is the de vicefor neutralizing the effect on the galvanometer of the earths magnetism,the bar a being turned byscrew s and held in any position by spring t.On the top of the box is thelanipsocket R, for holding lamp 13. It isinclined, as shown, so that the lamp will throw its light on the indexesand scales at the front of the box; also, by placing the lamp outsidethe box the size of the box may be much diminished. Thecircuit-connections are not shown in Fig. 3. The wires pass through thewood of the box. The connections will be readily understood from thepreceding explanations.

In operating the apparatus sleeve 6 is moved until thegalvanometer-needle stands at zero. "When any changes occur in theelectro-motive force in the circuit, such changes are seen upon thegalvanometer-scale, and the generators supplying current to the circuitare regulated in accordance with these indications. The variations mayalso be indicated by scale 2'. Vhen the galvanometer is deflected,resistance E is regulated so as to bring it back to zero, and the amountof such regulation indicated upon scale t shows what the amount ofchange of electro-motive force has been. This is the preferred way whenthe instrument is used as a temporary indicator to measure variousdifferent electro-motive forces. When the instrument is used as apermanent indicator, as in the station of an electric lighting system,to indicate variations from a standard electromotive force, thegalvanometer-scale is usually read.

Fig. 5 illustrates a form of apparatus by which a permanent record ofchanges of electro-motive force is obtained. The arrangement of circuitsand resistances is the same as already described. S is a cylinder,revolved by suitable clock-work or other mechanism, over which runs astrip, T, of chemically-prepared paper, such as is used with chemicaltelegraph-instruments. Upon the surface of the paper rest two metalpens, s ands, which are suitably supported, and one of which isconnected with the moving resistance-contact, and the other between theresistances in the opposite arm of the bridge, in the same manner as thegalvanometer is connected in the form previously described. It isevident that so long as there is no difference of potential betweenthese terminals there will be no marks made upon the paper; butwhencurrent flows across the bridge in one direction or the other onepen or the other, according to the direction of current, will leave amark upon the moving paper. This indicates the variations inelectro-motive force, and at the same time leaves a permanent recordwhich shows when the electro -motive force has been high or low and whenit has remained constant.

This form of instrument is well adapted for use on vessels where themotion may affect the ordinary indicator.

An additional advantage of using one lamp in the indicator instead oftwo is that any illcandescing electric lamp is liable to develop defectsin use, which make uncertain the indications dependent upon it. It isevident that with two lamps the liability to error in this way is justtwice as great as when only one is used.

\Vhat I claim is 1. In an electrical indicator, the combination of aresistance sensitive to changes in temperature and a resistancepractically constant under such changes in one side of a \Vheatstonebridge, and two such constant resistances in the other side, and a'current-in dicator connected between the two sides, substantially as setforth. I o

2. In an electrical indicator, the combination of an incandescingelectric lamp and a wire resistance in one side of a \Vheatstone IIObridge, two Wire resistances in the other side, and a current-indicatorconnected between the two sides, substantially as set forth.

3. In an electrical indicator, the combination of an incandescingelectric lamp and a wire resistance in one side of a Vheatstone bridge,three wire resistances in the other side, and a current-indicatorconnected between the two sides, one of whose terminals is connectedwith a contact adjustable upon the middle one of the three resistances,sub stantially as set forth.

at. In an electrical indicator, the combination of an incandescingelectric lamp and a high wire resistance in opposite sides of aWheatstone bridge, other resistances-one in each side-similarlyproportioned to the lamp and high wire resistances, and acurrent-indicator connected between the two sides, substantially as setforth.

JOHN XV. HOWELL.

Witnesses:

A. XV. KIDDLE, E. U. ROWLAND.

